How to Build A Roof Deck On A Pitched Roof

Blog August 21, 2020

There’s nothing like spending a relaxing afternoon on your very own roof deck. Whether your house is in a downtown district or the middle of the countryside, a rooftop deck gives you fantastic views in the comfort of your home.

However, building a rooftop deck can be challenging to do on your own, especially if you have a slanted roof. There are lots of critical things to consider, like the structural integrity of your roof with the added weight of the deck.

If you’re keen to take on this challenge, here are the steps for how to build a rooftop deck on a sloped roof.

Gather the needed materials

The essential first step for how to build a rooftop deck starts with getting the right materials.

The three most essential elements of a rooftop deck include the support beams, the deck framing, and the material for the deck itself. The beams are what makes building a level rooftop deck on pitched roofs possible. Get the most durable lumber you can find for this crucial element.

For the framing of the roof deck, you have several options. You can go with sleepers, which are inexpensive and come in a variety of materials like recycled plastic lumber. Wood can also be used, but tends to be heavy and has the danger of warping or rotting. The best framing on a rooftop deck on sloped roofs uses aluminum joists, which are durable and will not warp in any way.

Finally, decide on your deck’s material. Synthetics like composite wood or PVC are common and inexpensive materials. However, not all of them can withstand the harsh conditions of a rooftop deck, so further research is advised. For a more durable and lasting deck, high-density hardwood like Garapa or Machiche is recommended.  


Create a deck plan

A deck plan allows you to put down all of your rooftop deck ideas on paper and helps guide you throughout the building process. Aside from dimensions, you should also include the features of the deck, such as what furniture or overhead element you’ll use.

Having a detailed deck plan also helps you communicate your vision to third party contractors like roofers or structural engineers. It ensures things don’t get lost in translation.

Figure out if your roof can support the weight

Before you do anything, you should first figure out the loading capacity of your roof. This tells you if the roof can support all the added weight of your rooftop deck. You should also factor in the added furniture and people who will be using that deck since these add significant load.

Even if your roof can handle the weight, you need a plan to distribute that evenly while building a rooftop deck. For the best stability, place the support beams at the strongest areas of your roof and have the house’s foundation eventually bear all of that weight.

Load distribution is a crucial step that will be disastrous to get wrong, so it’s best to get the help of a professional roofing contractor or structural engineer.

Get the necessary permits and clearance

Before building a rooftop deck, check first if your neighborhood allows it. Some areas or municipalities have different zoning regulations and building codes that might prohibit a roof deck. Sometimes your neighborhood association might oppose it.

Even if it’s allowed in your area, you often need to secure a permit from your local building department before you start with construction. You might need to submit sloped roof deck plans signed by a licensed structural engineer as part of the requirements, so be ready with that.

Prepare the support beams and sill plates

Now comes the actual installation of your sloped roof deck. Begin by cutting your support beam and sill plates from your lumber as per the specifications of a structural engineer. 

For the sill plates, you’ll need around four pieces of 1-foot 2-by-6 lumber. 

For the support beam, the architect will provide specifications, but it will often be cut from a 4-by-10 piece of wood. Drill through the beams every 3 feet from the edge, then insert a galvanized lag bolt on each. Secure with a washer and nut at the back face of the lumber.

Attach the beams over the sill plates

Place a beam vertically over each pair of sill plates and then place a hold down on either side of the beam. Drill through the sill plate via the holes in the hold down, deep enough to allow a threaded rod to pass through. This holds the sill plate in place over the roof.

With the sill plate secure, put the beam between each hold down. Drill through the beam via the holes in the top arm of the hold down. Finally, secure the beam with a galvanized bolt, washer, and nut. Do this again with the other beam. You now have the two front support beams in place.

Repeat the process with the rear set of sill plates and support beams to complete your roof deck’s foundation.

Install the joist, framing, and deck boards

With the support beams properly installed, you can now proceed with installing your rooftop deck as you would on a flat roof. Attach the joists, framing, and deck boards as usual.

Ultimately, there are plenty of things that can go wrong with building your rooftop deck on a slanted roof. It’s much safer and easier just to trust a professional roofing company to do the job for you.

Professional roofing with JAE Construction

A company like JAE Construction is invaluable when you plan on doing a rooftop deck or any other roof-related project. Our Fort Lauderdale roofing team has over 20 years of experience working on countless South Florida homes and offices, so we can tackle any roofing task no matter how complicated. Contact us today for a free quote!